Single longitudinal mode operation of semiconductor lasers is a desirable property which can be obtained with distributed feedback structures as long as the feedback is obtained totally from the distributed structure and not from any cleaved end. Such lasers are disclosed in U.S. Pat. No. 3,675,157 issued July 4, 1972 to H. W. Kogelnik et al. Fabrication of distributed feedback lasers is difficult in some cases and their threshold currents have generally been found to be higher than for lasers with cleaved mirrors.
Another form of longitudinal mode control was disclosed by P. J. de Waard in his talk entitled "A Novel Single Mode Laser Having Periodic Variations in the Stripe Width ("Super DFB")" which was presented at the Optical Communications Conference in Amsterdam, Netherlands, Sept. 17-19, 1979. In the laser described by de Waard an electrode is used that has periodic stripe width variations in order to create a structure which is said to be similar to a succession of optical waveguides. In this way, de Waard states that he achieves a stable longitudinal mode behavior.